Conventionally, a control device that performs an automatic stop control in which operation (rotation) of an engine is automatically stopped when a predetermined automatic stop condition is satisfied for the purpose of improvement of fuel consumption of a vehicle carrying an engine and reduction of a quantity of exhaust gas discharged from the vehicle has been known.
Such a control device will re-start an engine automatically, when a demand for re-start of an engine occurs in a case where an accelerator pedal operation is made or in a case where a brakes operation is released. In this case, the control device re-starts an engine, for instance, by performing any of (1) a normal control, (2) an ignition start-up control, and (3) a starter start-up control, depending on an engine rotational speed at the time of occurrence of a re-start demand.
The ignition start-up control is performed when the engine rotational speed has been decreased to a level at which it is difficult to re-start the engine by the normal control (a fuel injection and an ignition during a normal operation) although the engine rotational speed has not reached “0 (zero)” completely. In accordance with the ignition start-up control, a fuel injection and an ignition are performed in a cylinder in an expansion stroke (hereafter, may be referred to as an “expansion stroke cylinder”) so that a cylinder in a compression stroke (hereafter, may be referred to as a “compression stroke cylinder”) can get over a top dead center of the cylinder.
By the way, in the ignition start-up, compression in the cylinder may become insufficient and inertia sufficient to re-start an engine may not be obtained after ignition even though a fuel injection and an ignition are performed at that time, when a piston of the expansion stroke cylinder is away from the top dead center. Therefore, a technology for certainly re-starting an engine by standing by until a rotational direction of the engine is inverted to a reversed rotational direction and performing a fuel injection and an ignition in an expansion stroke cylinder after the inversion (for instance, refer to Japanese Patent Application Laid-Open “kokai” No. 2005-163612 (JP2005-163612)).